Physical tape libraries have been used historically to store data, particularly in large scale data backup and retrieval systems. A physical tape library represents a collection of physical tapes (i.e., physical magnetic tapes). Often a physical tape library includes a large number of physical tapes, for example, thousands to hundreds of thousands of physical tapes. The physical tapes are housed and organized such that a robotic arm known as a picker can be used to select each physical tape from its slot and insert it into a physical tape drive under electronic control. The physical tape library may be coupled with a network and used for backup network data storage. Backup software applications and other software (e.g., on network coupled computers) may be configured to use such physical tape libraries.
One drawback to such physical tape libraries is that they rely on robotics and other mechanical components to function. As such, physical tape libraries tend to be relatively susceptible to malfunction (e.g., the robotic arms may break, the robot arms may drop physical tapes, etc.). However, existing backup applications and technology has been designed to use physical tape libraries. Often these backup programs are configured to interact with the physical tape libraries through the use of small computer system interface (SCSI) commands to direct the selection, loading, manipulation and writing of data to the physical tapes. Thus, recoding these programs to work with other types of storage systems would be costly and time consuming.
Virtual tape libraries provide an alternative to physical tape libraries. The virtual tape libraries appear to be physical tape libraries to the backup applications, and other software. These virtual tape libraries may emulate physical tape libraries including all of the SCSI commands utilized by the backup programs to interact with the physical tape libraries. However, the virtual tape libraries typically do not actually store the data on physical magnetic tapes, but rather store the data on one or more hard disk drive arrays, solid state storage devices, or other types of physical storage. This offers an advantage that the virtual tape libraries do not need to rely on the mechanical components, such as robotic arms used for physical tape libraries. Moreover, the backup applications, or other software utilizing the virtual tape library, do not need to know that physical magnetic tapes are not being used for data storage, and do not need to be changed. This helps to avoid modifying existing backup applications and technology that has been designed to use physical tape libraries. As a further advantage, the data stored by a backup application to a virtual tape may be stored as a file of a file system. As such, the virtual tape libraries are generally able to take advantage of advanced file system functionalities, such as improved ability to perform data deduplication, replication, redundancy, segmenting, and/or other file system based technologies.